linux-kernel - Re: [kvm-devel] [PATCH 0/2][KVM] guest time accounting

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Message-ID: <46C057C0.7020003@bull.net>
Date:	Mon, 13 Aug 2007 15:08:16 +0200
From:	Laurent Vivier <Laurent.Vivier@...l.net>
To:	Avi Kivity <avi@...ranet.com>
Cc:	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	virtualization <virtualization@...ts.linux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [kvm-devel] [PATCH 0/2][KVM] guest time accounting

Avi Kivity wrote:
> Laurent Vivier wrote:
>>> - perhaps the new fields should be guarded by a #ifdef CONFIG_HYPERVISOR
>>> (selected by CONFIG_KVM)?  that way the (minor) additional overhead is
>>> only incurred if it can possibly be used.  I imagine that our canine
>>> cousin will want to use this as well.
>>>     
>>
>> There is also a CONFIG_VIRTUALIZATION and a CONFIG_VIRT_CPU_ACCOUNTING
>> (from
>> s390 and powerpc) Which one to use ?
>>   
> 
> Are these options for using the kernel as a guest or host?  I'd guess
> the former.

I didn't find CONFIG_HYPERVISOR.
The good one seems to be CONFIG_VIRTUALIZATION that is used to activate CONFIG_KVM.

>> I'm wondering if we can have a more accurate accounting:
>>
>> - For the moment we add all system time since the previous entering to
>> the VCPU
>> to the guest time (and I guess there is some real system time in it ???)
>>
>> - Perhaps we can sum nanoseconds spent in the VCPU and add it to
>> cpustat when
>> these ns are greater than 1 ms ? (I'm trying to make something in this
>> way)
>>   

Ingo (or other guru), could you have a look to the attached patch, it is what I
was thinking about when I wrote this.

Laurent
-- 
------------- Laurent.Vivier@...l.net  --------------
          "Software is hard" - Donald Knuth

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